(1) Field of the Invention
The present invention relates to a semiconductor device in which a bypass lead portion connecting a non-adjacent lead and an electrode is included to provide a flexibility of wiring of leads and electrodes. The present invention relates to a method of producing the semiconductor device by using a lead frame to provide the flexibility of wiring of leads and electrodes. The present invention relates to a semiconductor device unit in which two or more semiconductor devices which are the same as the above semiconductor device are stacked to increase a packaging density.
(2) Description of the Related Art
There are demands for small-size, high-speed electronic units in recent years, and, in particular, semiconductor devices having smaller sizes and higher speeds are required. To provide small and high-speed semiconductor devices, it is desirable to increase the packaging density related to the semiconductor devices. As an attempt to increase the packaging density, a semiconductor device unit in which a plurality of semiconductor devices are located one above another is under development.
The number of electrode pads which can be provided on a single semiconductor chip is limited, and it is difficult to perform the wiring of leads and electrode pads on the semiconductor chip by using a known wiring technique, in order to realize a desired level of the packaging density.
It is desirable to provide a semiconductor device which allows a flexible wiring of leads and electrodes on the semiconductor chip. Also, it is desirable to increase the packaging density related to the semiconductor devices and provide a small-size electronic unit in which the semiconductor devices are included.
FIG. 1 shows a wire-bonded portion of a semiconductor device 1. In this semiconductor device 1, a conceivable lead connecting portion for connecting a lead and an electrode which are not adjacent is included.
Referring to FIG. 1, a semiconductor chip 2 is bonded to a die stage 3 in the semiconductor device 1. A plurality of electrode pads 4a through 4e are provided on the semiconductor chip 2. A plurality of leads 6 are electrically connected to the electrode pads 4a through 4e by wires 5.
The leads 6 include respective outer lead portions and respective inner lead portions 6a through 6e. The outer lead portions serve as external terminals of the semiconductor chip 2. The inner lead portions 6a-6e are electrically connected to the electrode pads 4a-4e on the semiconductor chip 2 via the wires 5. For the sake of simplicity, only the inner lead portions 6a-6e of the leads 6 on the semiconductor chip 2 are shown in FIG. 1.
The semiconductor device 1 includes a resin package 7 enclosing the semiconductor chip 2 and the wires 5, and partially enclosing the leads 6. These elements of the semiconductor device 1 are protected from the outside by the resin package 7.
In the semiconductor device 1, shown in FIG. 1, it is necessary to provide a lead connecting portion 8 in order to connect the non-adjacent lead 6b and electrode pad 4e. The lead connecting portion 8 includes a crossing piece extending along a side edge of the semiconductor chip 2, and includes an edge 8a adjacent to the electrode pad 4e on the semiconductor chip 2. The edge 8a of the lead connecting portion 8 is electrically connected to the electrode pad 4e by the wire 5.
The lead connecting portion 8 allows an electrical connection of the inner lead portion 6b and the electrode pad 4e which are not adjacent. Thus, the use of the lead connecting portion 8 provides a flexibility of the wiring of the leads and the electrodes for the semiconductor device 1.
It is conceivable to produce a semiconductor device unit in which various semiconductor devices of the type such as the above semiconductor device 1 are stacked one over another, in order to increase the packaging density related to the semiconductor devices. In this semiconductor device unit, each semiconductor chip of the semiconductor devices must have a chip-select electrode in order to select that semiconductor chip to be enabled or disabled. The chip-select electrode allows the complete semiconductor chip to be enabled or disabled according to a chip-select signal on the chip-select electrode.
In the semiconductor device 1, shown in FIG. 1, the electrode pad 4e is the above-mentioned chip-select electrode. This chip-select electrode is electrically connected to a predetermined lead (which is, for example, the lead 6b in FIG. 1) among the leads 6 of the semiconductor device 1.
There are several cases in which the chip-select lead and the chip-select electrode which are not adjacent must be connected to each other, because of the circuit layout of the semiconductor device unit. In such cases, the use of the lead connecting portion 8 allows the non-adjacent lead 6b and electrode 4e to be electrically connected to each other.
However, in the above semiconductor device 1, no supporting element which supports the lead connecting portion 8 is provided. When a relatively long lead connecting portion 8 must be included in the semiconductor device 1, a mechanical strength of the lead connecting portion 8 is inadequate and the lead connecting portion 8 tends to be deformed during the manufacture. For example, when the semiconductor device 1 is molded with the resin package 7 by a resin material, the lead connecting portion 8 may be deformed by the resin material during the molding process.
If the above lead connecting portion 8 is bent by the resin material, the lead connecting portion 8 may interfere with or damage the other leads 6c-6e or the wires 5 connecting the leads 6c-6e and the electrode pads 4c-4e. Thus, the reliability of the above semiconductor device 1 after the manufacture is relatively low.